As is well known, mixed convection and steam cooking is increasingly appreciated for the quality of the results obtained; in fact, it makes it possible to cook food, particularly meat and vegetables, in an organoleptic and dietetically optimal manner.
Convection and steam cooking ovens consist essentially of an external support casing, housing at least one food holding chamber, and are equipped with a control and monitoring unit for their operation.
This type of oven is generally equipped with three units of specific devices that have respectively the purpose of supplying heat for heating the atmosphere (air and steam) in the cooking chamber, circulating the atmosphere, and generating the steam inside the chamber.
In electrically heated ovens, the means to heat the atmosphere in the oven generally consist of electrical heating elements, while in gas-heated ovens these means consist of a gas combustion unit and a unit for exchanging the heat between the burning gas and the atmosphere in the oven.
The means for circulating the atmosphere in the oven normally consist of an electric fan unit and a shroud for circulating the atmosphere in a closed circuit within the cooking chamber.
The steam generating means can be instantaneous steam generators or, alternatively, dry saturated steam generators that can be applied in electric ovens as well as in gas ovens.
In ovens with an instantaneous steam generator, also called direct steam generator, or generators that can at times generate moist stream, or steam containing suspended liquid water droplets, steam production is achieved by nebulizing the water supplied by the water supply and blowing it against the heating elements.
In ovens with a dry saturated steam generator, also called ovens with boiler, steam production is generally achieved by using a suitable closed container (boiler) located externally with respect to the cooking chamber, wherein water is evaporated by electrical or gas means.
In general, the oven cooking of food requires very different methods according to the results and effects desired: an efficient control of the humidity in the cooking chamber makes it possible to achieve qualitatively optimal levels of food cooking, avoiding for example an excessive accumulation of water in the food and in the dishes, which would clearly effect their aesthetic appearance and organoleptic characteristics.
It should be emphasized that the term “humidity in the cooking chamber” is intended to mean relative humidity, measured in percentage terms, that expresses the relationship between the quantity of water vapor contained in the mass of air filling the cooking chamber and the maximum amount of water vapor (saturation) that the same mass of air can contain in the same conditions of temperature and pressure.
There are rather sophisticated measuring instruments known in the art that are capable of instantly and precisely detecting the percentage of humidity present in the oven: however, instruments of this type, in addition to being extremely costly, cannot operate at temperatures higher than 180° C., which characteristics make them absolutely unsuitable for use in an oven.
In addition, once the degree of humidity present in the cooking chamber has been measured, it is necessary to have systems that compare it with the level preset/desired by the user, or reference level, and, if necessary, that correct it by the introduction of vapor or air through appropriate known actuator devices.